Wills served as a volunteer nurse during World War I and as a pathologist during World War II.

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Friday's Google Doodle celebrates the 131st birthday of hematologist Lucy Wills, who discovered that folic acid can help prevent a life-threatening type of anemia in pregnant women.

Women in Mumbai in the 1920s were dying during pregnancy in alarming numbers, felled by a blood deficiency called anemia. Under the microscope, their red blood cells were swollen and enlarged, and they weren't carrying nearly enough hemoglobin, the protein in the blood that transports oxygen. Wills noticed a link between women's diets and their risk of anemia during pregnancy, and she realized that a shortage of one nutrient in particular was causing the deadly anemia -- she just had to figure out which nutrient.

In 1920s Mumbai, what people ate was closely tied not only to their socioeconomic class, but to their religion. So Wills studied the diets of women from different demographics in Mumbai, then went back to the lab and fed the same diets to rats and rhesus monkeys. Just as she'd noticed in her patients, the lab animals that ate diets low in vitamin B tended to suffer from anemia, and they usually died during pregnancy. But when she added yeast extracts to their food, it prevented -- and even cured -- anemia. She went back to the clinic and started feeding anemia patients a British breakfast spread called Marmite, which is made from yeast extract, and it worked.

Even then, Wills and her colleagues still weren't sure exactly which chemical compound in the Marmite actually did the trick. There are several types of B vitamins, and they're not interchangeable. Scientists had discovered vitamin B1, or thiamine, in 1926 (regular readers might recognize thiamine as the cure for beriberi), and they knew that vitamin B12 -- found in purified liver extracts -- helped treat a different kind of anemia, but it didn't help with condition menacing Mumbai's women. Scientists dubbed the unknown compound Wills Factor and kept on feeding pregnant women Marmite. It wasn't until the 1940s that chemists learned that Wills Factor was actually a type of B vitamin called folate, which you may have encountered in the form of folic acid.